Rb20Det - Forward Facing Plenum

[raZ1911]

Also needs a tune to make the most of it.

[Footnah]

After speaking to an engine builder and tuner, he's tuned plenty of RB20s with a FFP and has never seen a loss in power. The shorter runner length changes where the torque curve comes in the rev range but doesn't go backwards in power.

He actually had an a31 cefiro with a 20 and greddy FFP almost ready for the dyno and is going to keep me updated with the results. He also says the car becomes alot more responsive with the shorter length of piping and generates less turbo lag.

On the other hand, he said he has seen some after market plenums that have provided a very minimal difference, but still rates them due to the responsiveness, cleaner engine bay and accessibility.

I then went and got a second opinion from a very knowledgeable source who confirmed that there's no way I'll be going backwards.

Fitting it won't be an issue as I have the manifold off currently which is why I decided to research if FFP were better in the first place. Battery was going in the boot anyway and the cars getting a tune because I changed the turbo, exhaust and air flow metre.

[Ryno]

We're just trying to help mate... The advise you have got would only make sense if you were building a race car, as the on/off throttle response is definitely better with short runners. However in that case a race engine doesn't need torque down low, as the revs are always kept high.

Also don't confuse the throttle response you gain (due to the short runners and less intercooler piping) with increased turbo spooling. Your turbo will spool slower with short inlet runners as there is less torque down low and hence less exhaust gas to hit the turbo and help it build boost.

All the advice you've had in this thread has been sound. If your car is a daily drive, loosing inlet runner length is just stupid, especially with the RB20. For me if you must go to a front facing plenum, your best two options are to either modify you current plenum to change the throttle body location or buy a Plazmaman style plenum top to retain your lower runners.

Do I know what I'm talking about?

I have a RB25 in my car and swapped the standard plenum to this when I went to a front mount intercooler....

Any gains I made in throttle response, were rubbish compared to the loss of torque down low and lower spool rate of the turbo. So after 5 years of persisting with this plenum and getting different tunes to try to improve the driveability, I went back to the standard lower runners with a MX performance plenum top.

That lesson has wasted probably $2000 of my money.... We're not a performance shop trying to convince you to spend money, so we can profit from you.... We're trying to give you advice so you save money!

[stilettoman]

I am new to this forum, have never driven a Skyline, and my only experience with RB motors is with the RB20DET which I installed in my 1984 RX-7. However, we did modify the intake manifold, not for more performance but to get rid of the clutter on top of the motor. Before we even looked at the various intakes that are shown on the web, my fabricator friend cut up the stock intake and modified it as shown. He cut up an old Porsche 944 intake to get the pieces he wanted for a factory "cast" look.

The main point I want to make is that if you have the skills available, you can do this without changing the runner lengths. Of course the plenum volume has been significantly reduced. Everyone who has driven this thing seems to be impressed with the torque over the speed range.

[Dose Pipe Sutututu]

^ holy shit your mate has very impressive skills :wub: :woot: :woot:

[GTSBoy]

I like it when people do a god job of cutting up and rebuilding RB plenums like that. But I always end up wondering what the air distribution ends up like. Especially when the volume ends up reduced, not increased.

FWIW, the shape that that plenum has been given stands a good chance of having good distribution. But unless you either flow tested it, or better yet had 6 exhaust pyros installed, you really don't know.

[stilettoman]

"the shape that that plenum has been given stands a good chance of having good distribution. But unless you either flow tested it, or better yet had 6 exhaust pyros installed, you really don't know."

I agree completely. I retired from Boeing a few years ago after 36 years, B.S. and M.S. in aero engineering ( you may have heard of Boeing - they make those noisy things that occasionally fly over your house). Never worked as an aerodynamicist, but I think I understand the basics of airflow, also commonly known as black magic. But the advantage of a mod like this is you can test drive it, and if you have nothing better to do, dyno test it. I plan to install a wheel speed sensor for my friend's rally computer, and then I can get some pretty accurate horspower and torque curves.

There are other types of "performance mods" that cannot be easily tested. I have several friends who are very experienced, expert aerodynamicists, and the thing we most often laugh about over a beer is this amazing fad that has been going on for more than 40 years, and shows no signs of fading away. I refer of course to this idea of taking a really nice looking car and cluttering up the shape with a wing or spoiler on the back end. Without exception, all of my aero friends agree that 1. It may or may not produce any down force, but you will never know without some very difficult and expensive testing. 2. Only a tiny fraction of the people who do this for street use will ever go fast enough for the wing to make any noticeable difference.

Hope this tirade doesn't get me banned form the forum.

[GTSBoy]

Man, you need to step up your efforts if you want to risk getting banned.

I disagree about the utility of wings. Mine stands a good chance of keeping my boot lid shut if the catch fails while I'm driving around. Plus, it blocks up the screw holes that would be left if I took it off. Very useful things.

[Dose Pipe Sutututu]

not at all mate, comments and posts like that encourage thinking unlike forums like nissansilvia where it's just all garbage and retards

[raZ1911]

Also don't use a big throttle body if you do go with a plenum. Use the stock one, bigger will only make it crappy for street.

[StevenCJR31]

I am new to this forum, have never driven a Skyline, and my only experience with RB motors is with the RB20DET which I installed in my 1984 RX-7. However, we did modify the intake manifold, not for more performance but to get rid of the clutter on top of the motor. Before we even looked at the various intakes that are shown on the web, my fabricator friend cut up the stock intake and modified it as shown. He cut up an old Porsche 944 intake to get the pieces he wanted for a factory "cast" look.

The main point I want to make is that if you have the skills available, you can do this without changing the runner lengths. Of course the plenum volume has been significantly reduced. Everyone who has driven this thing seems to be impressed with the torque over the speed range.

i had a good look at those pics and that is automotive art at its best

[Footnah]

I am new to this forum, have never driven a Skyline, and my only experience with RB motors is with the RB20DET which I installed in my 1984 RX-7. However, we did modify the intake manifold, not for more performance but to get rid of the clutter on top of the motor. Before we even looked at the various intakes that are shown on the web, my fabricator friend cut up the stock intake and modified it as shown. He cut up an old Porsche 944 intake to get the pieces he wanted for a factory "cast" look.

The main point I want to make is that if you have the skills available, you can do this without changing the runner lengths. Of course the plenum volume has been significantly reduced. Everyone who has driven this thing seems to be impressed with the torque over the speed range.

I highly rate that!

I'm thinking modding the standard plenum is the way to go. Will have a good look at it this weekend and hopefully come up with something.

Edited July 19, 2013 by Footnah

[stilettoman]

"I'm thinking modding the standard plenum is the way to go. Will have a good look at it this weekend and hopefully come up with something."

My fabricator friend, Sean O'Brien, has come up with a concept you might want to consider - relatively simple if you have a good aluminum welder who can help you. Just make a plate that bolts to the lower manifold, and then weld on a cast aluminum V8 valve cover. Dozens of styles are available from very plain, no writing or logo to the old style with ribs cast in, some with names like Offenhauser or Edelbrock. The volume is about right, and the length will allow some over hang at the rear so the idle air valve can be hidden underneath if you want a clean look. The throttle body flange can be welded to the front, straight out or angled as required.

I like this RB20 so much I bought another complete R32 front clip when I had the chance, got one with 35,000 miles. Recently I found the car I have been looking for, in nice condition for a very good price. It is an iconic design, the first modern car made in the U.S. after WWII, fairly small, weighs only 2700 pounds, and is a 1948 model. As soon as Sean saw this, he said we have to make in intake that looks like a 50's hot rod part, and then he come up with the idea of using a valve cover. I soon found one with the appropriate name cast in, and had it shipped as-cast with no holes drilled. Photo attached. In case you think this is just another engine swap, be advised the level of insanity goes well beyond that. The complete R32 front structure will be grafted to the firewall and frame rails, so the entire front suspension will be Skyline. I also acquired an R33 rear suspension,which will fit nicely under the rear frame rails. Suffice it to say this will not be your grandfather's Studebaker. Don't mean to hijack this thread - I will start a topic in the Project section as soon as we begin the cutting and welding.

And those who appreciate our "automotive art" may want to look at this: www.cardomain.com/ride/646433

[TTT]

OP - Look for a build thread titled "A boy and his love for his RB20"

The crazy person that created that thread has a sick love for RB20s.

long story short... he was making over 260rwkw.

paid mega dollars for a good brand name FFP.

Had it fitted, cooler piping revised to suit.

back on the dyno and it was worse at everything other than pretty engine bay.

less power, less torque, more lag, more aidz everywhere.

go read it..

dyno results and all.

[Super Drager]

The only FFP i'd put on an RB20 is a GTR one with the ITB's tbh.

[Footnah]

The only FFP i'd put on an RB20 is a GTR one with the ITB's tbh.

That would be the dream.

What's required to fit them?

[StevenCJR31]

a lot of work. . .stud pattern is different and port size is also different

[Footnah]

If that's all I'll just make an adapter plate.

[JDD199]

Anyone running the Plazmaman plenum? I assume this is just the top bolt on replacement. So I don't have to muck around with the whole manifold etc.

How did you find the fitup? Any advice or things to look out for?

I figure I'd ask in here over creating a new thread. Have the RB20DET in the 32 and mainly looking to reduce the kilometres of pipe work in the engine bay. If i gain a little power then I'll call it a bonus.

Thanks

[GTSBoy]

I figure I'd ask in here instead of searching for the (no doubt) 800 threads in which the fitment of Plazmaman plenae have been discussed.

Fixed your post a bit.